He also backed Tan Sri Muhyiddin Yassin as the best candidate in the race for the Umno deputy presidency while suggesting that the other two challengers are involved in money politics.
"That's a good way to use ISA, not for some writer who writes nonsense," he said of corrupt Umno members and also in an apparent reference to Malaysia Today editor Raja Petra Kamarudin, who was released recently from ISA detention.
Dr Mahathir, who has become increasingly vocal in recent weeks, said there is "a strong possibility that Umno deputy presidential candidates are involved in money politics."
"Because some people who were at the bottom during the first week, suddenly shot up," said Mahathir when asked to comment whether the contest for the Umno deputy presidency is tainted with money politics.
The contest for the party's deputy presidency is now a three way tussle between Muhyiddin, who garnered 92 nominations, Datuk Seri Ali Rustam and Tan Sri Muhammad Muhd Taib.
Ali and Muhammad received the minimum nominations, 39 on the last weekend of the Umno divisional meetings. Ali now has 48 nominations while Muhammad, 45.
"Everybody knows that Umno leaders are using money, when the election comes, the people will reject them. Not everyone is but the majority is. So you can be an Umno leader, but the people will reject you. When we have lost, there is no point in becoming Umno president," said Mahathir.
"Who wants to elect somebody who bought his way up," he added
"When you know somebody who has got very bad history and still getting support. That history I think has relevance to the support," he said when asked about the three cornered fight for the deputy presidency.
However he said among all the three candidates, Muhyiddin is the most qualified.
He recommended that all party leaders be investigated and removed from the party if found guilty.
"We need to clean up the party. Now you see the opposition is very quiet and Umno is seen as a very corrupt party, so opposition will talk about how they are not corrupt," said Mahathir.
He said that Umno leaders who are involved in money politics should be thrown into prison.
ARef: Che Det nih semenjak dua menjak nih, lain macam aje bunyi suaranya.... sekejap duk habaq Bangsa Malaysia boleh jadi Pi Em lah.... sekarang laks mintak di ISA ahli2 UMNO yang perasuah...... aku nak tanya, PEMANGKU PKNS KAT SELANGOR YANG BANGSA MALAYSIA DARIPADA KAUM CINA tuh..... Ok tak Det???? Lagi satu, kalau budak bawah nih (gambar)... PERASUAH.... sanggup ke DET tengok?????